1. Field of the Invention
The present invention relates generally to flat panel displays, and particularly to a two-dimensional position-detecting user input device, and more particularly to an electromagnetic digitizer for a flat panel display.
2. Description of Related Art
Flat panel displays, such as liquid crystal displays (LCD), are becoming ubiquitous for displaying images. One type of LCD is provided with a two-dimensional position-detecting user input device (i.e., a digitizer) to allow user input, such as user interactivity with respect to images displayed (e.g., selecting an icon), handwriting recognition, drawing, cursor control, etc. This type of LCD is often referred to as a “touch panel” LCD. The digitizer may be based on sensing mechanisms such as resistive sensing, capacitive sensing, infrared sensing, acoustic wave sensing, force sensing, electromagnetic sensing, etc.
For an electromagnetic touch panel, the underlying operational principle is magnetic induction. There are three main components for magnetic inductive input, including a two dimensional sensor array, an electromagnetic pen, and a controller operatively coupled to the sensor array and the electromagnetic pen. The electromagnetic pen acts as a signal transceiver, the sensor array acts as a signal receiver, and the controller determines the two-dimensional coordinates of the pen with respect to the sensor array by detecting the current change as a result of magnetic induction in the sensor array caused by a change in magnetic flux brought about by the pen. As a result, as the pen is moved about with respect to the sensor array, the two-dimensional coordinates of the pen (i.e., X-Y coordinates) relative to the display surface can be determined by the controller. Electromagnetic digitizers provide relatively accurate position detection of the pen, in relatively good resolution compared to some of the other forms of sensing mechanisms.
Heretofore electromagnetic digitizers have been implemented in a flat panel display by simply by assembling a discrete digitizer module with a display module. FIG. 1 schematically illustrates a conventional flat panel display 500 having a flat panel display module 502 (e.g., an LCD module) and a separate electromagnetic digitizer board 504 assembled in a stack. For example, the digitizer board 504 is attached to one planar surface of the display module 502. A controller 508 is operatively coupled to the digitizer board 504 and a complementary electromagnetic pen 506. The digitizer board 504 includes a sensor array, which is formed by conventional printed circuit technology, with sensor array structures fabricated by printing technology. Printed circuit technology involves relatively large physical sizes and low resolution, as compared to semiconductor circuit fabrication technology. The sensor array includes metal conductive lines with a line width on the order of several hundred micrometers, as compared to semiconductor fabrication technology, involving line width on the order of micrometers. To achieve the desired sensitivity, the physical dimension of the sensor array tends to be relatively bulky. Further, given that the conventional electromagnetic digitizer board 504 is a separate and discrete component attached to the display module 502, it adds to the thickness and weight of the overall flat panel display 500.
It is therefore desirable to design and develop an electromagnetic digitizer that can be implemented in a relatively low form factor in a flat panel display, with improved sensitivity.